A solution of ethanol (C₂H₅OH) in water is 15.0% ethanol by weight. The molality of this solution is:

Question

Quizplus · Accepted Answer

To calculate the molality of a solution, we need to know the moles of solute per kilogram of solvent.

First, we need to convert the percent by weight of ethanol to grams of ethanol per 100 grams of solution:
15.0 g ethanol / (100 g solution)

Next, we need to convert the grams of ethanol to moles:
15.0 g ethanol x (1 mol / 46.07 g) = 0.326 mol ethanol

Finally, we need to calculate the mass of water in the solution:
100 g solution - 15.0 g ethanol = 85.0 g water

And convert this to kilograms:
85.0 g water x (1 kg / 1000 g) = 0.0850 kg water

Now we can calculate the molality of the solution:
molality = moles of solute / mass of solvent (in kilograms)
molality = 0.326 mol / 0.0850 kg
molality = 3.83 m

Therefore, the answer is B) 3.83 m.

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A Solution of Ethanol (C₂H₅OH) in Water Is 15